I’ve tried to enable CAN on my BeagleBone Green board. I had to stop the work before verification, because my logic analyzer is unavailable now. I record what I did in this article to make things reproducible when the logic analyzer is back.
There are several helpful links:
http://www.embedded-things.com/bbb/enable-canbus-on-the-beaglebone-black/
http://electronics.stackexchange.com/questions/195416/beaglebone-black-can-bus-setup
Readings to understand device tree overlay:
Device Tree for Dummies:
http://events.linuxfoundation.jp/sites/events/files/slides/petazzoni-device-tree-dummies.pdf
Device Tree Overlays (in adafruit)
https://learn.adafruit.com/introduction-to-the-beaglebone-black-device-tree/device-tree-overlays
Here are what I did:
# make a workspace
root@beaglebone:~# mkdir can
root@beaglebone:~# cd can
root@beaglebone:~/can# pwd
/root/can
# check if CAN is enabled ... no
root@beaglebone:~/can# dmesg | grep can
# take backup of the original device tree blob file for CAN
root@beaglebone:~/can# cp /lib/firmware/BB-CAN1-00A0.dtbo BB-CAN1-00A0.dtbo.orig
# make the device tree overlay
root@beaglebone:~/can# vi BB-DCAN1-00A0.dts
root@beaglebone:~/can# cat !$
cat BB-DCAN1-00A0.dts
/dts-v1/;
/plugin/;
/ {
compatible = "ti,beaglebone", "ti,beaglebone-black";
/* identification */
part-number = "dcan1pinmux";
fragment@0 {
target = <&am33xx_pinmux>;
__overlay__ {
dcan1_pins_s0: dcan1_pins_s0 {
pinctrl-single,pins = <
0x180 0x12 /* d_can1_tx, SLEWCTRL_FAST | INPUT_PULLUP | MODE2 */
0x184 0x32 /* d_can1_rx, SLEWCTRL_FAST | RECV_ENABLE | INPUT_PULLUP | MODE2 */
>;
};
};
};
fragment@1 {
target = <&dcan1>;
__overlay__ {
#address-cells = <1>;
#size-cells = <0>;
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&dcan1_pins_s0>;
};
};
};
# install the new device tree blob for CAN
root@beaglebone:~/can# dtc -O dtb -o BB-DCAN1-00A0.dtbo -b 0 -@ BB-DCAN1-00A0.dts
root@beaglebone:~/can# ls
BB-CAN1-00A0.dtbo.orig BB-DCAN1-00A0.dtbo BB-DCAN1-00A0.dts
root@beaglebone:~/can# cp BB-DCAN1-00A0.dtbo /lib/firmware/
root@beaglebone:~/can# cmp BB-DCAN1-00A0.dtbo /lib/firmware/BB-DCAN1-00A0.dtbo
# add the device
root@beaglebone:/lib/firmware# cat /sys/devices/platform/bone_capemgr/slots
0: PF---- -1
1: PF---- -1
2: PF---- -1
3: PF---- -1
root@beaglebone:~/can# echo BB-DCAN1 > /sys/devices/platform/bone_capemgr/slots
root@beaglebone:~/can# cat !$
cat /sys/devices/platform/bone_capemgr/slots
0: PF---- -1
1: PF---- -1
2: PF---- -1
3: PF---- -1
4: P-O-L- 0 Override Board Name,00A0,Override Manuf,BB-DCAN1
# check dmesg ... looks fine
root@beaglebone:~/can# dmesg | tail -n15
[ 25.499860] wlan0: send auth to 00:1d:73:33:47:a0 (try 1/3)
[ 25.522620] wlan0: authenticated
[ 25.524815] wl18xx_driver wl18xx.2.auto wlan0: disabling HT/VHT due to WEP/TKIP use
[ 25.528911] wlan0: associate with 00:1d:73:33:47:a0 (try 1/3)
[ 25.538576] wlan0: RX AssocResp from 00:1d:73:33:47:a0 (capab=0x431 status=0 aid=4)
[ 25.764831] wlan0: associated
[ 25.765114] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[ 26.579282] wlcore: Association completed.
[ 3395.588267] bone_capemgr bone_capemgr: part_number 'BB-DCAN1', version 'N/A'
[ 3395.588337] bone_capemgr bone_capemgr: slot #4: override
[ 3395.588380] bone_capemgr bone_capemgr: Using override eeprom data at slot 4
[ 3395.588425] bone_capemgr bone_capemgr: slot #4: 'Override Board Name,00A0,Override Manuf,BB-DCAN1'
[ 3395.613523] bone_capemgr bone_capemgr: slot #4: dtbo 'BB-DCAN1-00A0.dtbo' loaded; overlay id #0
[ 3395.648848] CAN device driver interface
[ 3395.689001] c_can_platform 481d0000.can: c_can_platform device registered (regs=fa1d0000, irq=192)
# load CAN modules
root@beaglebone:~/can# sudo modprobe can
root@beaglebone:~/can# sudo modprobe can-dev
root@beaglebone:~/can# sudo modprobe can-raw
root@beaglebone:~/can# lsmod | grep can
can_raw 5852 0
can 28397 1 can_raw
c_can_platform 6602 0
c_can 9577 1 c_can_platform
can_dev 11663 1 c_can
# Startup the CAN interface. Set CAN channel rate 500kbps.
root@beaglebone:~# ip link set can0 up type can bitrate 500000
root@beaglebone:~# ifconfig can0
can0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
UP RUNNING NOARP MTU:16 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:10
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
Interrupt:192
# Check the device status. Status UNKNOWN doesn't sound right...
root@beaglebone:~/can# ip -d -s link show can0
4: can0: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN mode DEFAULT group default qlen 10
link/can promiscuity 0
can state ERROR-ACTIVE (berr-counter tx 0 rx 0) restart-ms 0
bitrate 125000 sample-point 0.875
tq 500 prop-seg 6 phase-seg1 7 phase-seg2 2 sjw 1
c_can: tseg1 2..16 tseg2 1..8 sjw 1..4 brp 1..1024 brp-inc 1
clock 24000000
re-started bus-errors arbit-lost error-warn error-pass bus-off
0 0 0 0 0 0
RX: bytes packets errors dropped overrun mcast
0 0 0 0 0 0
TX: bytes packets errors dropped carrier collsns
0 0 0 0 0 0
Then I have to stop here.